The two key features of federalism are:

(i) There are two or more levels of government and the governments at different levels should agree to some rules of power sharing.

(ii) They should also trust that each would abide by its part of the agreement. The constitutionally granted powers of jurisdiction are thus unable to be changed by any single level. They require the consent of all government levels.

An ideal federal system has both aspects: mutual trust and agreement to live together.